Schistosoma mansoni control in Cul de Sac Valley Saint Lucia. II Chemotherapy as a supplement to a focal mollusciciding programme

After an intensive area-wide mollusciciding campaign, over four and a half years, transmission of Schistosoma mansoni was reduced. A cheaper scheme suitable for the follow-up or consolidation stage of control was evaluated and two selective population chemotherapy campaigns using hycanthone (2 mg/kg b.w.) and oxamniquine (15mg/kg b.w.) were mounted. Prevalence dropped to 6 percent and 3 percent in areas with previously high and low levels of transmission respectively. Calculations suggested that these figures were falsely low and that perhaps 20 percent of the population were still excreting S. mansoni ova in small numbers. The unco-operative groups in the population are probably more important in maintaining a reservoir of infection in the community than persons with light infections undetected by the sedimentation concentration stool examination technique used. The benefit of more sensitive but more costly examination techniques is not clear since the importance of very light infections in transmission is uncertain. Case detection absorbs an increasing proportion of the total cost of chemotherapy programmes with fewer cases being found amongst the same number screened. Using hycanthone (649 treated) the cost per person protected was $0.74 and using oxamniquine (264 treated) $0.94. The need to develop low cost consolidation or follow-up procedures for preventing a resurgence of transmission after successful control, when the infection is no longer of public health importance, is stressed. (AU)

Control of Schistosoma mansoni transmission by chemotherapy in St. Lucia. I. Results in man

Control of Schistosoma mansoni transmission solely by treatment of all infected persons was attempted in Marquis Valley (population about 3,100), St. Lucia. Two-year results are reported. Excluding 26 pregnant patients, 709 of 729 persons who were found to be infected received treatment the first year. Most of these, 677, were given a single injection of hyacanthone (2.5 mg/kg of body weight), and the same treatment was administered to 159 patients the second year. Side effects were not severe; the major side effect, vomiting, occurred in about 22 percent on both occassions. In villages with initially high transmission rates, the incidence of new infections in children 0 to 14 years fell from 20.8 percent before chemotherapy to 7.4 percent after 1 year and to 3.7 percent after 2 years. This pattern was significantly different from that in the comparison area where no control scheme exists. Chemotherapy alone appears to ba a rapid, effective, and comparatively inexpensive method of controlling S. mansoni transmission in St. Lucia (AU)